How to Reset a Mini-Split: Power Cycle, Remote Reset and Manual Button

Which reset do you need?

Power cycle reset, step by step

1. Turn the unit off with the remote. Mitsubishi warns not to switch the breaker off or on during operation because it may create sparks; switch the unit off with the remote first.
2. Turn off the mini-split's breaker at the panel, or its outdoor disconnect if it has one.
3. Wait with the power off. Carrier recommends about 20 minutes (Carrier). Fujitsu's and Mitsubishi's manuals don't give a wait time, so use your own brand's guidance if it has one.
4. Turn the breaker back on.
5. Wait about 3 minutes. Fujitsu says the compressor won't operate for about 3 minutes after the power goes off and on suddenly, to protect the circuit. Mitsubishi says the unit can't be operated for about 3 minutes when restarted.
6. Turn it on with the remote and check the mode and setpoint.

Fujitsu's manual describes exactly this fix for one common case: if other electrical devices or a nearby radio transmitter cause the unit to malfunction, turn off the circuit breaker once, turn it back on, and resume operation with the remote (Fujitsu General).

Don't be surprised if the unit starts on its own when power comes back. Both manuals describe an auto-restart function that resumes the previous mode after a power interruption. On Fujitsu units, a blinking TIMER light afterward just means the timer needs to be set again.

Resetting the remote

On Mitsubishi's MSZ-AP remotes, the setup steps are to install new AAA alkaline batteries and then press the Reset button gently with a thin instrument. The manual says the remote may not work correctly if Reset isn't pressed (Mitsubishi Electric). Set the clock again afterward. Other brands differ, so check your remote's manual for a reset or initial setting procedure.

Running the unit without the remote

Indoor units usually have a small button for this, though the name and behavior differ by brand.

On Fujitsu's ASU9RL2 and ASU12RL2, the MANUAL AUTO button works by how long you hold it:

Avoid the 10-second hold. Fujitsu marks forced cooling as for servicing only.

On Mitsubishi's MSZ-AP, the emergency operation switch (E.O. SW) cycles through emergency cooling, emergency heating and stop each time you press it, at a set temperature of 24 °C (75 °F) with medium fan. The first 30 minutes are a test run with temperature control off and the fan on high.

When a reset isn't the answer

Some behavior looks like a fault but isn't. Fujitsu says that in HEAT mode the indoor unit can stop for up to 15 minutes while the OPERATION light blinks during automatic defrost. Mitsubishi notes heating can stop for up to about 10 minutes for defrost. If you can see frost or ice on the outdoor unit, read Ice on Your Heat Pump: Normal Frost or a Problem? before you reset anything.

Stop resetting and call for service when:

• Mitsubishi: the operation indicator lamp blinks (outside of normal defrost), water leaks or drips from the indoor unit, the breaker trips frequently, you hear abnormal sounds, or refrigerant leakage is found.
• Fujitsu: the unit smells of burning or emits smoke, water leaks from the unit, or the OPERATION and TIMER indicators blink while the ECONOMY indicator blinks fast. Turn off the breaker and contact authorized service personnel.

Carrier also says that if the problem comes back after a reset, the system may need professional diagnosis. A breaker that keeps tripping is on Mitsubishi's list of reasons to stop and call, so don't keep switching it back on.